Concentration of oxidized iron ores



Patented Dec. 12, 1944 zssmrs concam'raarron or oxnuznn mom cans Earl H. Brown and Francis X.

Mimn, assignors to Min Tartaron, Hibbing,

erals Separation North American Corporation, New York, N. Y, a corporation'of Maryland No Drawing. Application February 25, 1944. Serial No. 523,924

16 Claims.

This invention relates to the concentration of iron ores and more particularly to the concentration of finely-divided low grade iron ores in which the iron is present as one of the several oxides of iron or as the carbonate of iron, and in which the gangue is principally silica or quartz.

In our copending application, Serial No. 496,- 582, filed July 29, 1943. we have described a method of concentrating finely-divided oxidized iron ores in which the gangue ingredient is principally quartz, which consists in treating an aqueous pulp of such an ore with an anionic collecting agent selected from the class consisting of higher fatty acids and resin acids and mix tures of fatty and resin acids and soaps thereof, and with cooperating agents consisting of lime and an aqueous solution of gelatinized starch; and subjecting the thus treated ore pulp to frothflotation treatment and removing the quartzcontaining froth, thereby producing in the residue of the pulp an oxidized-iron concentrate. In the methods described in that prior application, the starch preferably was gelatinizcd by boiling it in water with caustic soda: but examples were included in which the method utilized starch which had been gelatinized merely by boiling it in an aqueous suspension, or without heating by merely agitating a mixture of starch and caustic soda in an aqueous suspension.

The present invention is the result of our further discovery that highly satisfactory results may be obtained in practicing the said method with an aqueous solution of acid-treated starch. We have found that the best results are obtained by treating the starch with an acidic compound in an aqueous mixture, particularly when the pH of the said solution is low. This discovery resulted from extensive research and tests from which the conclusion appears justified that when acid-treated starch is employed, best results are obtained when the aqueous solution of starch and acid has a pH lower than 3.0, and preferably ranging from about 1.6 to about 2.2. Furthermore, our research and tests seem to lead to the conclusion that, when acid salts are employed in treating the starch, best results are obtained in practicing the method when the pH of the aqueous solution of starch and acid salt is kept at the lowest practical pH, and the results of the method grow poorer as the pH of the aqueous solution of starch and acid salt increases. It is not essential, however, that the pH of the starch soluthe ore pulp be lower than as used in this specification we intend to include both colloidal and molecular dispersions. Measurements of pH were made on the aqueous solution of acid-treated starch at room temperature, employing a Beckman pH meter, model M.

Our experiments seem to have proved also that the acid-treatment of the starch can best be carried out by boiling only briefly a mixture of the starch and acidic compound with water; although we have succeeded in acid-treatment of the starch in a mixture with water without boiling, in a manner hereinafter described in Example XII. We have found that best results are obtained if the mixture of starch, acidic compound and water is treated only enough to cause partial depolymerization and make the starch miscible with water. but not so as to form degradation products of the nature of dextrin, which seem to give only feeble results in practicing the method of concentration. In general, boiling of the said mixture for only about one minute has been found to produce a satisfactory acid-treated starch solution.

V of these mixtures In producing the aqueous solution of acidtreated starch employed in the examples hereinafter described, we have successfully used the following typical inorganic acidic compounds: sulphuric acid, hydrochloric acid, nitric acid, ferric ammonium chloride, ferric ammonium sulphate, ferric chloride, ferric sulphate, hydrofluoric acid and stannic chloride. In the treatment of the starch. we have also successfully used typical organic acidic compounds, such as tartaric acid and oxalic acid.

The anionic collecting reagents useful in the present methods are the same as those described as useful in the method described in the aforesaid copending application, namely, those selected from the class consisting of higher fatty acids and resin acids and mixtures of fatty and resin acids, and soaps thereof. Examples are hereinafter given of the use, as anionic collecting agents in practicing the invention, of a mixture of fatty that which is produced as making and sold under the soap made by neutralization of acids; sodium resinate: sodium oleate; linoleic acid; fish-oil fatty acid; and rosin acid. In some cases, we have found it advantageous to dilute these collecting agents, particularly Varlacoid,"

name "Varlacoid;

operation.

We have also proved that the method may be given.

be understood from the following description of examples of the practicing themed. In all of the the oxidizedm I imnore feedwlswash elasifl overflow from which an a m which was plus 100 mesh was out, ground t ough 100 mesh nd In practicing the invention with starch treated added to the minus 100 mesh ortion, thereby 5 t su p u a an a LM t e b t results r m afeedwhichwns all minus 100 mesh. were obtained when the p p ons of starch An aqneflll pulp 0! this feed, containing about to sulphuric acid were 97-3, which produced a pH soiidawaecondiflmed with the anionic colof 2.0 in the aqueous acid-treated starch soluiectina agents and with tion. The results of the cooperating agents this test were as follows:

ofan onoflime and 10 the aqueous solutkn o! acid-treated starch; after Per cent pulp was subjected 3213: r? m cm g?" theresidueofthisflrntfmth l t i 1 was further conditioned with additional quantig:

ties of said reagents, subjected to froth-flotation Concentr te no no. us m2 8:. 2

t. and the silica-containing froth was removed and w: In some cases, the residue of the second truth-flotation treatment was further conditioned by the addition of one or more or the said reagents, was subjected to froth- Comparative, less efficient but still satisfactory results using greater and less proportions of sulphuric acid to starch-in the making of the aqueous acid-treated starch solution, were as folflotation, and the silica-containing froth was relows: movedanddiscarded. Thepulpwas agitated for about one minute after the addition of each Concentrate reagent. The rmidue of the aforesaid treatments Ho r H was the oxidised-iron concentrate. P Per cent Per cent E I l h 1 acid r r P rea igents were a e: diffeze e e Bu p m 0 mg; 0 an? glam misery examples being in the kind of acidic compound 30 employed and im pro ortion to the starch which KZIZIIIIZII hi 2%.? 1%.: wasmmtreated as a 2% mixture in water by boiling the f o starch. acidic compound and water E n Starch treated with hydrochloric acid In practicing the invention with starch treated with hydrochloric acid (sp. gr. 1.18), the best results were obtained when the prop rtions of starchto hydrochloric acid were 97-3, which produced a pH of 2.2 in the aqueous acid-treated starch solution. The results of this test were as proportion of the acidic compound the lower the pH and vice versa, for acidic compound. That will be tfromthedatahereinaitergivenregardins test: of the method. The lime employed mthewasinfliefonnofa25%sus- 1on0. inwater. Theanioniccoilectinsrcagent I to XI was a mixture of arlacoid cresylic acid in the prop rtions of Per cent 95 parts of the former to 5 parts of the latter. Inga RIF? New 'lhequanfiflesotused. lnlbs. per ton of feed, were follows: FM mg no no set a as as is M as 50.79 as! 81.7 aM-a Comparative. less emcient but still satisfactory l n I H Mn. is results using greater and less proportions of hydrochlorlcacidtostarchmthemakinsottho fiueous acid-treated starch solution. were as fol- I! Beelmd float on concentrate Ami-Ii. is m P In... 1.00 luiphurlc acid a; Percent re cant VWIHMM- use M Fe silic m as o-r.-- 1.8 an ass ass sat 00-1. as ms nu nus no M Third float v a I M m m m Starch treated wlthnitric ma Ofcom'saflie otandthe-mannerof Inpracticingthelnventionwithstarchtreated oddilll therelgmilandthennmberof flotation with nitric acid (sp. gr. 1.42), the best results mas varied without departing were obtained when the pro or starch to fruntheqiritandseopeoltheinrention. nitricacidwereW-3,whichproducedapHot22 asoam 3 in the aqueous acid-treated starch solution. The Comparative. less eflloient but still satisfactory remiltsotthistcstwereastollows: resnltsusingalesll mportionot ferrlcammomumsulphatetortarchinthemalringof the t eous starch solution, were as follows: mt? r? a ls: m

0mm 2.12 m. um's it a: saw: s "cc. 3 or 4c 17 u ma m 60.67 am as:

' 03-7 2. 35 8. 9 52. 8 l6. B 70. 6 t but still satisfactory P oportions of nitric of the aqueous acldv! follows= Starch trusted with 1mm chloride cmmm In practicing the invention with starch treated Promo 0' with ferric chloride, the best results were obstarchto pH Per cm tamed when the proportions of starch to ferric weight 3 3 re chloride were 93-! which produced a pH of 1.9 in M! the aqueous acid-treated starch solution. The

results of this test were as follows: 93-! 1.7 315 68.01 7.00 85.4 90-1 2.5 8.8 57.02 8.! 71.7 P rum 8 Exams: IV Mm 131% Parr?"- pgiam Starch treated with ferric ammonium chloride M0 M0 In practicing the invention with starch treated 3-2 a: with ferric ammonium chloride, the best results as 4.8 were obtained when the proportions of starch to that acidic compound were 93-7 which produced a pH of 1.9 in the aqueous acid-treated starch solution. The results of this test were as follows:

Per cent Per cent Per cent Per cent Product weight Fe Feglecov.

Feed 100. 0 21. 77 Ill). 0 First iroth. 68. 0 3. 74 0. 9 Second iroth l0. 6 10.00 4. 9 Third froth. l. B 39. M 2. 9 Concentrate. 29. B 60. 08 82. 3

Comparative, less efllclent but still satisfactory nium chloride to starch in the making of the aqueous starch solution, were as follows:

Concentrate Proportion of r r i to PE P t P 1 or e ammosr can or can nium chloride weight of 1 32 Fe feed recovery Exams: V

Starch treated with ferric ammonium sulphate In practicing the invention with starch treated with ferric ammonium sulphate (iron and ammonium sulphate, purified), the best results were obtained when the proportions or starch to that acidic compound were 85-15 which produced a pH of 2.2 in the aqueous acid-treated starch solution. The results of this test were as follows:

Per cent Per cent Per cent Per cent weight Fe silica 10). 0 21. 52 100. 0 34. 9 3. 96 ii. 4 8. 0 7. l0 9. 4 8. 7 2h. 02 Ii. 3 28. 4 66. 23 72 0 Comparative, less eillcient but still satisfactory results using less proportions of ferric chloride to starch in the making of the aqueous starch Starch treated with ferric sulphate In practicing the invention with starch treated with ferric sulphate, the best recovery was obtained when the proportions of starch to ferric sulphate were 93-7 which produced a pH of 2.2 in the aqueous acid-treated starch solution.

The results of this test were as follows:

Using a greater proportion of ferric sulphate to starch in the making 01' the aqueous starch solution, the results were as follows:

6mm m 0 a H 9 Per cent Per t ferric sulphate: weight or Per gsnt Paruignt feed recovery 4 eserve WVIII acidtostsrchhithemskinsotthesqueous starch solution. were as follows: Starch treated with hydrofluoric acid Omeentr te In the invention with starch treated 5 mm of with hydrofluoric acid (48% solution). the best stardlto p11 "out mt results were obtained when the proportions of m want at f g fif Fe men to acid were 85-15 which produced a r! or m 2.2 in the aqueous acid-treated starch solution. 1 a m 7 'lheresultsofthletestwerensiollowsz 10 M Percent Per cent per cent n "we Fe silica "f?" Starch treated with oxalic acid 1 In practlcinl the invention with starch treated -3} with oxalic acid, when the proportions o! starch also 1017 to oxalic acid were 85-15 which produced a. pl! 11 of 1.! in the aqueous acid-treated starch solution, the results were as follows:

Comparative. less ei'iicient but still satistac- P t t Per cent tor! results usinx a less proportion of said acid Pmdw feign I? i il fg tostsrchinthemskinaoitheaqueousstarch sohitiomwereastollows: "no mm 64.8 5.90 17.8 :2 a ti 0mm ccncmtm. ao's 50.08 n1 mpcrflm a starch to H hydroflmrll acid 9 Pa cent 1, mm Per cent ig F, fg Usingsless proborflonoioxnlicacidtostarch $0 in the making at the aqueous starch solution. "-1 1 15 319 51 86 l 8L7 the I --v 1. IX Concentrate m Proportlonoi to PH Pa cent Per cent Starch treated with stannic chloride "mm of g? gf gf r leed recovery In practicing the invention with starch treated with stannic chloride, the iollowing results were iii-7 M 3M obtained when the proportions of starch to sten- 4 nlc chloride were 93-7 which produced a. oi! oi! 1.8 in the aqueous acid-treated starch solution.

w XII Starch treated with acid without boilin In the foregoing examples, "ashereinheiore Page? Psr e ent P A- can 531533,. stated, the starch was treated by boiling it with I an acidic compound in an dqueous mixture. The present example demonstrates that the invention g; 1 23-; may be practiced with starch which has been 15.: 11.34 treated with an acidic compound without hoilinz 2-: 2? 25 grams otdrystsrchwerecoveredwltha'l%% hydrochloric acid solution and allowed to r at room temperature (24' C.) for 7 days during mm x which themixturewasstirred threetimessday.

F5 The thus treated starch was filtered, then starch treated with, g mm w with alcohol until free of acid, and was dried at C. The product thus obtained was made In practicing the invention with starch treated up as a 2% solution in water. and in that torm were as follows; first flotation treatment only 1.5 lbs. (instead of 2.5 lbs.) of the aqueous acid-treated starch was used. The results or the treatment were as fol- PMM Per our? Perrcsint Fe rm Per cent Per oent mm Product m 6 F3 nov- Im- 0 13. 73 1m. 0 48- G 2. 8 7. 3 l5- 4 4. 7D 1. 6 0. I 18. 25 G. 1 a. I 57- at 81l- 0 secure Item XIII Sodium rcsinate as the collecting agent m M M Acid-heatedstarah collecting agent employed was amixture otvarla- 5 Lime cold and cresylic acid. In the tests about to be feed, were as follows: a m

, Dbl Llnoloio acid G. 8

Reagents First float As heretofore, the oxidized-iron ore feed was all MW M w minus 100 mesh and was conditioned in an aque- Llme.... to one pulp containing about 10% solids. The remm sults are given below:

4 Percent mb Beoundiloet so Product mm Faggota s-95 NWNGQ Second (rot 7. 71

Third froth.-- 24 29.39-

25 Ooncentrate.. 29.2 new na e: Third float Exam: XV

Fatty acid as the collecting aoent mm M In this example, the procedure was the same as in Example XIV except that Upiolm's fatty Th following table shows th excellent results acid whlch is a flshofl may was as obtained by practicing th invention using 80,, the anionic collecting agent. 'I'he result were dium resinate as the anionic collecting agent, as follow with cooperating agents consistin of lime and starch treated with sulphuric acid or lrvdrochloric Product Per em Per cent g g acid or nitric acid, the proportions of starch to rr acid being indicated in parentheses alter the name oicach acid: 40 Food moo 21.42 moo First froth--- 68.4 no me emits it #2; it own!" Concentrate: I: 30, 7 so: as 82. 3 Acid used in sel inizing 2 Pa m ,833,331 Exmu XVI Rosin as the collecting agent sul uric acid 2.0 are a1, 81 30.4 In this example the procedures were the same N do g'gag fig 33-2 as in Example XIV, except that the anionic collecting ent was rosin dissolved as a 20% solution in aniline, and except that the quantities It will be noted that these results compare faor rosin employed were only 0.3 lb. in the first vorably with the results set forth in Examples float, 0.2 lb. in the second float and 0.1 1b. in I. I! and III, in which the anionic collecting the third float. The results wereasfollows: ageirt was a mixture of Variacoid and cresylic aci Emma: XIV Product 2% E? 5:52:- Linoleic acid as the collecting agent Feed moo 21.83 man In this example, the anionic collecting agent gfiiifiifissii :3: it; 2% 1? employed was linoleic acid: the starch was treat- Third 14 ed with Sulphuric acid in 97-3 proportions and was used in an aqueous solution, as hereinbefore described and the lime Exams XVII Sodium olecte as the collecting agent In this example, the anionic collecting agent was sodium oleate which was employed as a 1% aqueous solution; the starch and sulphuric acid (sp. gr. 1.84) were in the proportions of 97-3 in a 2% aqueous solution which was boiled for one minute as heretofore; the lime was in the form of a 25% suspension in water as heretofore: and the oxidized-iron ore feed was minus it!) mesh an was initially conditioned with the ama 'rhuuem reagents in a pulp the examples hereinbefore ins time prior to each flotation step was about one minute; and the quantities of reagents used, inlbs. per ton of feed. were as follows:

containing 10% solids as in given. The condition- Multan Pa'omt W llremt Percent h in Ill. IL ma 4.62 11.8 12-0 9.1 518 10.1

The results of this test were as follows:

. Per cent Per cent Per cent Product eight Fe Fe m l-gov ma 0 21. 33 1(1). 0 38. 9 1 77 6. 0 4. 56 4. 6 10. 91 L 3. 5 66- 33 86. 9

Varlacoid soap as the collecting agent conditions were the same that a Varlacoid soap was used instead 01 sodium oleate, in the amounts of 0.5 1b., 0.25 lb. and 0.25 lb. per ton of feed in the three flotation operations. The Varlacoid soap was prepared by heating to 85 C. and slowly adding with constant stirring. was completely soluble, aqueous solution. The

Yer Per cent Per cent weigh F Fe recov- Actd-tr eated yellow cornmeal as the starch This example demonstrates that the invention may be practiced with yellow cornmeal as the starch-bearing material. The cornmeal was boiled for ten minutes with sulphuric acid (sp. gr. 1.84) in the ratio 0! 93-7 and as a 2% suspension in water, which are given in the table just preced- L The results of thetest were as tioo!93-Iandasa2%suspend0n and the quantities o1 reagent used were the same. Theresultsoithemwereastollowsz m "Ff results from the acidified water at a which the starch granules burst, otter which the acidified water is lowed by drying of the market product.

thetrentedstarchtoproduce Boilinsoifl-initflnaflk aqueous solution for one minute resultslnthepnchlceotourp-ocemaswillap- 45 peartromtheiollowlnlremlfisotatestinwhich the quantities of and methods used were the same as those hereinbefom inst precedinsExnmpleL n q Produd e also sue me as an 1.5 4.1: u 2. ans an hadheenboiledlnanaquellll phurlc acidmtheraflo weresubstantialbthesame.

starch has been treated 2. A method according to claim 1, in which the treatment of the starch with an acidic compound produces an aqueous solution or starch having a. pH below 3.

3. A method according to claim 1, in which the treatment of the starch with an acidic compound produces an aqueous solution of starch having a pH ranging from about 1.6 to about 2.2.

4. A method according to claim 1, in which the starch has been treated with an acidic compound only sumciently to produce partial depolymerization and not dextr 5. A method according to claim 1, in which the by boiling it with an acidic compound in an aqueous mixture.

6. A method according to claim 1, in which the starch has been treated by boiling it with an acidic compound in an aqueous mixture only long enough to produce partial depclymerization and not dextrln.

7. A method according to claim 1, in which the starch has been treated by boiling it with an acidic compound in an aqueous mixture for only about one minute.

8. A method according to claim 1, in which the starch has been treated by boiling it with an inorganic acid compound in an aqueous mixture.

9. A method according to claim I. in which the starch has been treated by boiling it with an organic acid compound in an aqueous mixture.

10. A method according to claim 1, in which thestarch hasbeen treatedbyb'oilingitwith sulphuric acid in an aqueous mixture.

11. A method according to claim 1, in which the starch has been treated by boiling it with sulphuric' acid in an aqueous mixture only long enough to produce partial depolyrnerization and not dextrin.

12. A method according to claim 1, in which the starch has been treated by boiling it with sulphuric acid in an aqueous mixture for only about one minute.

13. A method according to claim 1, in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture.

14. A method according to claim 1. in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture only long enough to produce partial depolymcrimtion and not dextrin.

15. A method according to claim 1. in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture for only about one minute. V

16. A method according to claim 1, in which the acid-treated starch has been neutralized.

EARL H. BROWN. FRANCIS K TARTAMN.

CERTIFICATE or CORRECTlON.

Patent p36hg7780 December 12, 19M.

EARL H. B30401, II AL- It is hereby certified that error appears in the printed specification a 4 of the above numbered patent requiring correction as follows: Page 2, secand 001mm, lines 60 to 63, ample II, for Proportion of of starch to h in the heading to the second table under Exetarch to sulphuric acid" read --Proportion rochlorlc acid--;. and that the said Letters Patent should be read with this correction therein that the same may conform to the record oi the case in the Patent orrice. I ammo and sealed this 20th day or March, A. 'n. 1915.

(Seal) Leslie Frazer Acting Commissioner of Patents.

starch has been treated 2. A method according to claim 1, in which the treatment of the starch with an acidic compound produces an aqueous solution or starch having a. pH below 3.

3. A method according to claim 1, in which the treatment of the starch with an acidic compound produces an aqueous solution of starch having a pH ranging from about 1.6 to about 2.2.

4. A method according to claim 1, in which the starch has been treated with an acidic compound only sumciently to produce partial depolymerization and not dextr 5. A method according to claim 1, in which the by boiling it with an acidic compound in an aqueous mixture.

6. A method according to claim 1, in which the starch has been treated by boiling it with an acidic compound in an aqueous mixture only long enough to produce partial depclymerization and not dextrln.

7. A method according to claim 1, in which the starch has been treated by boiling it with an acidic compound in an aqueous mixture for only about one minute.

8. A method according to claim 1, in which the starch has been treated by boiling it with an inorganic acid compound in an aqueous mixture.

9. A method according to claim I. in which the starch has been treated by boiling it with an organic acid compound in an aqueous mixture.

10. A method according to claim 1, in which thestarch hasbeen treatedbyb'oilingitwith sulphuric acid in an aqueous mixture.

11. A method according to claim 1, in which the starch has been treated by boiling it with sulphuric' acid in an aqueous mixture only long enough to produce partial depolyrnerization and not dextrin.

12. A method according to claim 1, in which the starch has been treated by boiling it with sulphuric acid in an aqueous mixture for only about one minute.

13. A method according to claim 1, in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture.

14. A method according to claim 1. in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture only long enough to produce partial depolymcrimtion and not dextrin.

15. A method according to claim 1. in which the starch has been treated by boiling it with hydrochloric acid in an aqueous mixture for only about one minute. V

16. A method according to claim 1, in which the acid-treated starch has been neutralized.

EARL H. BROWN. FRANCIS K TARTAMN.

CERTIFICATE or CORRECTlON.

Patent p36hg7780 December 12, 19M.

EARL H. B30401, II AL- It is hereby certified that error appears in the printed specification a 4 of the above numbered patent requiring correction as follows: Page 2, secand 001mm, lines 60 to 63, ample II, for Proportion of of starch to h in the heading to the second table under Exetarch to sulphuric acid" read --Proportion rochlorlc acid--;. and that the said Letters Patent should be read with this correction therein that the same may conform to the record oi the case in the Patent orrice. I ammo and sealed this 20th day or March, A. 'n. 1915.

(Seal) Leslie Frazer Acting Commissioner of Patents. 

